Unclustered tracers remain unclustered: the lack of primordial non-Gaussianity response of bias-zero tracers
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT)（能源、环境与技术研究中央中心）；Departamento de Física Teórica, Universidad Autónoma de Madrid（马德里自治大学理论物理系）；Department of Astrophysics, University of Vienna（维也纳大学天体物理学系）；Centro de Investigación Avanzada en Física Fundamental (CIAFF), Universidad Autónoma de Madrid（马德里自治大学基础物理高级研究中心）；Instituto de Física, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理研究所）
Celia Merino, Santiago Avila, A. G. Adame, A. Anguren, V. Gonzalez-Perez, J. Meneses-Rizo
Constraining primordial non-Gaussianities (PNG) is one of the main goals of new-generation large-scale galaxy surveys. It had been proposed that unclustered tracers (with bias $b_1=0$) could be optimal for PNG studies, and that these could be found by selecting galaxies in bins of their local density. Here, we test this hypothesis in state-of-the-art simulations from the PNG-UNITsim suite with local $f_{\rm NL}=100$ and $f_{\rm NL}=-20$. We consider different parent tracer catalogues: all halos together, halos in large mass bins, and HOD models for LRGs and QSO. We then classify these tracers by their local density ($δ_{t,R}$) and measure the linear bias ($b_1$) and PNG-response ($b_ϕ$). Most $δ_{t,R}$ bins show a PNG-response compatible with $b_ϕ=0$ for all halos or the low-mass bin (log$M<11$). For high-mass halos (log$M>$12), QSO or LRG, we recover a trend closer to the universality relation ($b_ϕ= 2 δ_{\rm crit}(b_1-1)$) for $b_1>1$, but the $b_ϕ(b_1)$ curve flattens to 0 below $\vert b_1\lvert<1$. Hence, we find $b_ϕ\approx0$ for all bias-zero tracers considered. The complex $δ_{t,R}$-based selection causes their clustering to strongly deviate from simple assumptions, namely the universality relation and Poisson shot noise, hindering their capability to constrain PNG.
We develop a new method to constraint primordial non-Gaussianities of the local kind using unclustered tracers of the Large Scale Structure. We show that in the limit of low noise, zero bias tracers yield large improvement over standard methods, mostly due to vanishing sampling variance. We propose a simple technique to construct such a tracer, using environmental information obtained from the original sample, and validate our method with N-body simulations. Our results indicate that $σ_{f_{\mathrm{NL}}^{\mathrm{loc}}}\simeq1$ can be reached using only information on a single tracer of suffici…
Tighter constraints on measurements of primordial non-Gaussianity will allow the differentiation of inflationary scenarios. The cosmic microwave background bispectrum-the standard method of measuring the local non-Gaussianity-is limited by cosmic variance. Therefore, it is sensible to investigate measurements of non-Gaussianity using the large-scale structure. This can be done by investigating the effects of non-Gaussianity on the power spectrum on large scales. In this study we forecast the constraints on the local primordial non-Gaussianity parameter $f_{\rm NL}$ that can be obtained with fu…
Local non-Gaussianity causes correlations between large scale perturbation modes and the small scale power. The large-scale CMB signal has contributions from the integrated Sachs Wolfe (ISW) effect, which does not correlate with the small scale power. If this ISW contribution can be removed, the sensitivity to local non-Gaussianity is improved. Gravitational lensing and galaxy counts can be used to trace the ISW contribution; in particular we show that the CMB lensing potential is highly correlated with the ISW signal. We construct a nearly-optimal estimator for the local non-Gaussianity param…
Large-scale Fourier modes of the cosmic density field are of great value for learning about cosmology because of their well-understood relationship to fluctuations in the early universe. However, cosmic variance generally limits the statistical precision that can be achieved when constraining model parameters using these modes as measured in galaxy surveys, and moreover, these modes are sometimes inaccessible due to observational systematics or foregrounds. For some applications, both limitations can be circumvented by reconstructing large-scale modes using the correlations they induce between…
We explore the use of different radio galaxy populations as tracers of different mass halos and therefore, with different bias properties, to constrain primordial non-Gaussianity of the local type. We perform a Fisher matrix analysis based on the predicted auto and cross angular power spectra of these populations, using simulated redshift distributions as a function of detection flux and the evolution of the bias for the different galaxy types (Star forming galaxies, Starburst galaxies, Radio-Quiet Quasars, FRI and FRII AGN galaxies). We show that such a multi-tracer analysis greatly improves …
We study the detectability of large-scale velocity effects on galaxy clustering, by simulating galaxy surveys and combining the clustering of different types of tracers of large-scale structure. We employ a set of lognormal mocks that simulate a $20.000$ deg$^2$ near-complete survey up to $z=0.8$, in which each galaxy mock traces the spatial distribution of dark matter of that mock with a realistic bias prescription. We find that the ratios of the monopoles of the power spectra of different types of tracers carry most of the information that can be extracted from a multi-tracer analysis. In pa…
We forecast future constraints on local-type primordial non-Gaussianity parameter $f_{\rm NL}$ with a photometric galaxy survey by Euclid, a continuum galaxy survey by Square Kilometre Array (SKA), and their combination. We derive a general expression for the covariance matrix of the power spectrum estimates of multiple tracers to show how the so-called multitracer technique improves constraints on $f_{\rm NL}$. In particular we clarify the role of the overlap fraction of multiple tracers and the division method of the tracers. Our Fisher matrix analysis indicates that stringent constraints of…
Estimators for weak lensing observables such as shear and convergence generally have non-linear corrections, which, in principle, make weak lensing power spectra sensitive to primordial non-Gaussianity. In this paper, we quantitatively evaluate these contributions for weak lensing auto- and cross-correlation power spectra, and show that they are strongly suppressed by projection effects. This is a consequence of the central limit theorem, which suppresses departures from Gaussianity when the projection reaches over several correlation lengths of the density field, L_P~55 [Mpc/h]. Furthermore, …
Primordial non-Gaussianity (PNG) is a key probe of the origins of primordial fluctuations in the early universe. It has been shown that multi-tracer measurements of large-scale structure can produce high-precision measurements of PNG. Future line intensity mapping surveys are well-suited to these measurements owing to their ability to rapidly survey large volumes and access the large scales at which PNG becomes important. In this paper, we explore for the first time how multi-tracer PNG measurements with intensity mapping surveys depend on the sub-galactic scale physics which drives line emiss…
Local primordial non-Gaussianity using cross-correlations of DESI tracers
Ohio University（俄亥俄大学）；The Ohio State University（俄亥俄州立大学）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Boston University（波士顿大学）；Università degli Studi di Milano（米兰大学）；INAF-Osservatorio Astronomico di Brera（INAF-布雷拉天文台）；University College London（伦敦大学学院）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）；CEA, Université Paris-Saclay（法国原子能委员会，巴黎萨克雷大学）；University of Rochester（罗切斯特大学）
Correlations between intrinsic galaxy shapes on large-scales arise due to the effect of the tidal field of the large-scale structure. Anisotropic primordial non-Gaussianity induces a distinct scale-dependent imprint in these tidal alignments on large scales. Motivated by the observational finding that the alignment strength of luminous red galaxies depends on how galaxy shapes are measured, we study the use of two different shape estimators as a multi-tracer probe of intrinsic alignments. We show, by means of a Fisher analysis, that this technique promises a significant improvement on anisotro…
We show how cross-correlating a high redshift external tracer field, such as the 21cm neutral hydrogen distribution and product maps involving Cosmic Microwave Background (CMB) temperature and polarisation fields, that probe mixed bispectrum involving these fields, can help to determine the reionization history of the Universe, beyond what can be achieved from cross-spectrum analysis. Taking clues from recent studies for the detection of primordial non-Gaussianity (Munshi & Heavens 2010), we develop a set of estimators that can study reionization using a power spectrum associated with the bisp…
One of the main signatures of primordial non-Gaussianity of the local type is a scale-dependent correction to the bias of large-scale structure tracers such as galaxies or clusters, whose amplitude depends on the bias of the tracers itself. The dominant source of noise in the power spectrum of the tracers is caused by sampling variance on large scales (where the non-Gaussian signal is strongest) and shot noise arising from their discrete nature. Recent work has argued that one can avoid sampling variance by comparing multiple tracers of different bias, and suppress shot noise by optimally weig…
Upcoming galaxy redshift surveys promise to significantly improve current limits on primordial non-Gaussianity (PNG) through measurements of 2- and 3-point correlation functions in Fourier space. However, realizing the full potential of this dataset is contingent upon having both accurate theoretical models and optimized analysis methods. Focusing on the local model of PNG, parameterized by $f_{\rm NL}$, we perform a Monte-Carlo Markov Chain analysis to confront perturbation theory predictions of the halo power spectrum and bispectrum in real space against a suite of N-body simulations. We mod…
Next-generation galaxy surveys will be able to measure perturbations on scales beyond the equality scale. On these ultra-large scales, primordial non-Gaussianity leaves signatures that can shed light on the mechanism by which perturbations in the early Universe are generated. We perform a forecast analysis for constraining local type non-Gaussianity and its two-parameter extension with a simple scale-dependence. We combine different clustering measurements from future galaxy surveys -- a 21cm intensity mapping survey and two photometric galaxy surveys -- via the multi-tracer approach. Furtherm…
Relativistic effects in clustering observations have been shown to introduce scale-dependent corrections to the galaxy over-density field on large scales, which may hamper the detection of primordial non-Gaussianity $f_\textrm{NL}$ through the scale-dependent halo bias. The amplitude of relativistic corrections depends not only on the cosmological background expansion, but also on the redshift evolution and sensitivity to the luminosity threshold of the tracer population being examined, as parametrised by the evolution bias $b_\textrm{e}$ and magnification bias $s$. In this work, we propagate …
In this note we examine the derivation of scale-dependent bias due to primordial non-Gaussianity of the local type in the context of general relativity. We justify the use of the Poisson equation in general relativistic perturbation theory and thus the derivation of scale-dependent bias as a test of primordial non-Gaussianity, using the spherical collapse model. The corollary is that the form of scale-dependent bias does not receive general relativistic corrections on scales larger than the Hubble radius. This leads to a formally divergent correlation function for biased tracers of the mass di…
Galaxy sizes as complementary (zero-)bias tracers of local primordial non-Gaussianity
Center for Data-Driven Discovery, Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学数据驱动发现中心，Kavli宇宙学前沿研究所（WPI），UTIAS）；Institute For Interdisciplinary Research in Science and Education, ICISE（ICISE跨学科科学研究与教育学院）；Theory Center, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK)（高能加速器研究机构（KEK）粒子核研究理论中心）；Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所引力物理与量子信息研究中心）；Korea Institute for Advanced Study（韩国高等研究院）
We study synergies between HI 21cm and H$α$ intensity map observations, focusing on SKA1-like and SPHEREx-like surveys. We forecast how well such a combination can measure features in the angular power spectrum on the largest scales, that arise from primordial non-Gaussianity and from general relativistic effects. For the first time we consider Doppler, Sachs-Wolfe and integrated SW effects separately. We confirm that the single-tracer surveys on their own cannot detect general relativistic effects and can constrain the non-Gaussianity parameter $f_{\rm NL}$ only slightly better than Planck. U…
We develop optimised estimators of two sorts of power spectra for fields defined on the sky, in the presence of partial sky coverage. The first is the cross-power spectrum of two fields on the sky; the second is the skew spectrum of three fields. These can probe the Integrated Sachs Wolfe Effect (ISW) at large angular scales and the Sunyaev Zéldovich (SZ) effect from hot gas in clusters at small angular scales. The skew spectrum, recently introduced by Munshi & Heavens (2009), is an optimised statistic which can be tuned to study a particular form of non-Gaussianity, such as may arise in the e…
Primordial non-Gaussianity encodes valuable information about the physics of inflation, including the spectrum of particles and interactions. Significant improvements in our understanding of non-Gaussanity beyond Planck require information from large-scale structure. The most promising approach to utilize this information comes from the scale-dependent bias of halos. For local non-Gaussanity, the improvements available are well studied but the potential for non-Gaussianity beyond the local type, including equilateral and quasi-single field inflation, is much less well understood. In this paper…
After reionisation, the 21cm emission line of neutral hydrogen within galaxies provides a tracer of dark matter. Next-generation intensity mapping surveys, with the SKA and other radio telescopes, will cover large sky areas and a wide range of redshifts, facilitating their use as probes of primordial non-Gaussianity. {Previous works have shown that the bispectrum can achieve tight constraints on primordial non-Gaussianity with future surveys that are purposely designed for intensity mapping in interferometer mode}. Here we investigate the constraints attainable from surveys operating in single…
We study the large-scale bias parameter of cosmic voids with primordial non-Gaussian (PNG) initial conditions of the local type. In this scenario, the dark matter halo bias exhibits a characteristic scale dependence on large scales, which has been recognized as one of the most promising probes of the local PNG. Using a suite of $N$-body simulations with Gaussian and non-Gaussian initial conditions, we find that the void bias features scale-dependent corrections on large scales, similar to its halo counterpart. We find excellent agreement between the numerical measurement of the PNG void bias a…
A wide range of multifield inflationary models generate non-Gaussian initial conditions in which the initial adiabatic fluctuation is of the form (zeta_G + g_{NL} zeta_G^3). We study halo clustering in these models using two different analytic methods: the peak-background split framework, and brute force calculation in a barrier crossing model, obtaining agreement between the two. We find a simple, theoretically motivated expression for halo bias which agrees with N-body simulations and can be used to constrain g_{NL} from observations. We discuss practical caveats to constraining g_{NL} using…
Multiple tracers of the cosmic density field, with different bias, number and luminosity evolution, can be used to measure the large-scale properties of the Universe. We show how an optimal combination of tracers can be used to detect general-relativistic effects in the observed density of sources. We forecast for the detectability of these effects, as well as measurements of primordial non-Gaussianity and large-scale lensing magnification with current and upcoming large-scale structure experiments. In particular we quantify the significance of these detections in the short term with experimen…
Extracting the bispectrum information from the large scale structure observations is challenging due to the complex models and the computational costs to measure the signal and its covariance. Recently, the skew spectrum was proposed to access parts of the bispectrum information with a more effective way and has been confirmed it can provide complementary information to that enclosed in the power spectrum measurements. In this work, we generalize the theory to apply the multitracer technique and explore its ability to constrain the local type primordial non-Gaussianity. Using the spectra and t…
We study the peculiar velocities of density peaks in the presence of primordial non-Gaussianity. Rare, high density peaks in the initial density field can be identified with tracers such as galaxies and clusters in the evolved matter distribution. The distribution of relative velocities of peaks is derived in the large-scale limit using two different approaches based on a local biasing scheme. Both approaches agree, and show that halos still stream with the dark matter locally as well as statistically, i.e. they do not acquire a velocity bias. Nonetheless, even a moderate degree of (not necess…
Large-scale clustering of highly biased tracers of large-scale structure has emerged as one of the best observational probes of primordial non-Gaussianity of the local type (i.e. f_{NL}^{local}). This type of non-Gaussianity can be generated in multifield models of inflation such as the curvaton model. Recently, Tseliakhovich, Hirata, and Slosar showed that the clustering statistics depend qualitatively on the ratio of inflaton to curvaton power ξafter reheating, a free parameter of the model. If ξis significantly different from zero, so that the inflaton makes a non-negligible contribution to…
The statistical properties of the primordial perturbations contain clues about the origins of those fluctuations. Although the Planck collaboration has recently obtained tight constraints on primordial non-gaussianity from cosmic microwave background measurements, it is still worthwhile to mine upcoming data sets in effort to place independent or competitive limits. The ionized bubbles that formed at redshift z~6-20 during the Epoch of Reionization are seeded by primordial overdensities, and so the statistics of the ionization field at high redshift are related to the statistics of the primord…
Unbiased analysis of primordial non-Gaussianity: the multipoles of the full relativistic power spectrum
Queen Mary University of London（伦敦大学玛丽女王学院）；University of Western Cape（西开普敦大学）；Università degli Studi di Torino（都灵大学）；INFN – Istituto Nazionale di Fisica Nucleare, Sezione di Torino（意大利国家核物理研究所都灵分部）；INAF – Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）
We explore possibility of using the three dimensional bispectra of the Ly-alpha forest and the redshifted 21-cm signal from the post-reionization epoch to constrain primordial non-Gaussianity. Both these fields map out the large scale distribution of neutral hydrogen and maybe treated as tracers of the underlying dark matter field. We first present the general formalism for the auto and cross bispectrum of two arbitrary three dimensional biased tracers and then apply it to the specific case. We have modeled the 3D Ly-alpha transmitted flux field as a continuous tracer sampled along 1D skewers …
We investigate the possibility of constraining primordial non-Gaussianity using the 3D bispectrum of Ly-alpha forest. The strength of the quadratic non-Gaussian correction to an otherwise Gaussian primordial gravitational field is assumed to be dictated by a single parameter fnl. We present the first prediction for bounds on fnl using Ly-alpha flux spectra along multiple lines of sight. The 3D Ly-$α$ transmitted flux field is modeled as a biased tracer of the underlying matter distribution sampled along 1D skewers corresponding to quasars sight lines. The precision to which fnl can be constrai…
We investigate the constraints on primordial non-Gaussianity with varied bispectrum shapes that can be derived from the power spectrum of galaxies and clusters of galaxies detected in future wide field optical/near-infrared surveys. Having in mind the proposed ESA space mission \emph{Euclid} as a specific example, we combine the spatial distribution of spectroscopically selected galaxies with that of weak lensing selected clusters. We use the physically motivated halo model in order to represent the correlation function of arbitrary tracers of the Large Scale Structure in the Universe. As naiv…
Multiple tracers of the same surveyed volume can enhance the signal-to-noise on a measurement of local primordial non-Gaussianity and the relativistic projections. Increasing the number of tracers comparably increases the number of shot noise terms required to describe the stochasticity of the data. Although the shot noise is white on large scales, it is desirable to investigate the extent to which it can degrade constraints on the parameters of interest. In a multi-tracer analysis of the power spectrum, a marginalization over shot noise does not degrade the constraints on $f_\text{NL}$ by mor…
Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), combining the information via multi-tracer cross-correlations that suppress cosmic variance on ultra-large scales. In order to fully incorporate wide-angle effects and redshift-bin cross-correlations, together with lensing magnification and other relativistic effects, we use the angular power spectra, $…
Primordial black holes (PBHs) are theoretical black holes which may be formed during the radiation dominant era and, basically, caused by the gravitational collapse of radiational overdensities. It has been well known that in the context of the structure formation in our Universe such collapsed objects, e.g., halos/galaxies, could be considered as bias tracers of underlying matter fluctuations and the halo/galaxy bias has been studied well. Employing a peak-background split picture which is known to be a useful tool to discuss the halo bias, we consider the large scale clustering behavior of t…
Cross-correlations between Cosmic Microwave Background (CMB) temperature and $y$-spectral distortions anisotropies have been previously proposed as a way to measure the local bispectrum parameter $f_{\rm NL}^{\rm loc.}$ in a range of scales inaccessible to either CMB ($T$, $E$) bispectra or $T$-$μ$ correlations. This is useful e.g. to test scale dependence of primordial non-Gaussianity. Unfortunately, the primordial $y$-T signal is strongly contaminated by the late-time correlation between the Integrated Sachs Wolfe and Sunyaev-Zel'dovich (SZ) effects. Moreover, SZ itself generates a large noi…
We present a derivation of two-point correlations of general tracers in the peak-background split (PBS) framework by way of a rigorous definition of the PBS argument. Our expressions only depend on connected matter correlators and "renormalized" bias parameters with clear physical interpretation, and are independent of any coarse-graining scale. This result should be contrasted with the naive expression derived from a local bias expansion of the tracer number density with respect to the matter density perturbation δ_L coarse-grained on a scale R_L. In the latter case, the predicted tracer corr…
Forthcoming radio continuum surveys will cover large volumes of the observable Universe and will reach to high redshifts, making them potentially powerful probes of dark energy, modified gravity and non-Gaussianity. Here we extend recent works by analyzing the general relativistic (GR) corrections to the angular power spectrum. These GR corrections to the standard Newtonian analysis of the power spectrum become significant on scales near and beyond the Hubble scale at each redshift. We consider the continuum surveys with LOFAR, WSRT and ASKAP, and examples of continuum surveys with the SKA. We…
Exploring Gravitational Wave Signatures Due to Primordial Non-gaussianity and Large Scale Structure Using SKAO
National Institute for Chemical Physics and Biophysics（国家化学物理与生物物理研究所）；Gran Sasso Science Institute（格兰萨索科学研究所）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））
Local non-Gaussianities in the initial conditions of the Universe, parameterized by $f_{\rm NL}$, induce a scale-dependence in the large-scale bias of halos in the late Universe. This effect is a promising path to constrain multi-field inflation theories that predict non-zero $f_{\rm NL}$. While most existing constraints from the halo bias involve auto-correlations of the galaxy distribution, cross-correlations with probes of the matter density provide an alternative channel with fewer systematics. We present the strongest large-scale structure constraint on local primordial non-Gaussianity th…
The impact of our peculiar motion on primordial non-Gaussianity measurements using the LIGER4GAL framework
Università di Padova（帕多瓦大学）；INFN Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；Università di Trieste（的里雅斯特大学）；INAF, Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；INFN, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；IFPU, Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；INAF, Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Argelander-Institut für Astronomie（阿尔根德天文学研究所）
The presence of additional particles during inflation leads to non-Gaussianity in late-time correlators of primordial curvature perturbations. The shape and amplitude of this signal depend on the mass and spin of the extra particles. Constraints on this distinct form of primordial non-Gaussianity, therefore, provide a wealth of information on the particle content during inflation. We investigate the potential of upcoming galaxy surveys in constraining such a signature through its impact on the observed galaxy power spectrum. Primordial non-Gaussianity of various shapes induces a scale-dependen…
Improving constraints on primordial non-Gaussianity from Quaia with a new cosmological observable: angular redshift fluctuations
Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉古纳大学）；MTA–CSFK Lendület “Momentum” Large-Scale Structure (LSS) Research Group（匈牙利科学院-斯洛伐克科学院 Lendület “Momentum” 大尺度结构研究组）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与教育网络天文学与地球科学研究中心）；University of Oxford（牛津大学）
